1. Field of the Invention
This invention relates to a molded face mask made of multiple layers in a manner that enhances comfort for the user.
2. Description of the Related Art
Disposable face masks are widely used in hospitals and medical and dental offices to reduce exposure to potentially hazardous bodily fluids or other contaminants that may become airborne. One type of such masks is the non-molded mask termed "flat mask" such as shown in U.S. Pat. Nos. 4,941,470, 4,802,473, 4,195,629, 2,458,580 and 1,292,095. Flat masks are relatively comfortable but may collapse during inhalation and enable a portion of the mask to contact the wearer's mouth and nasal openings. Consequently, there is a risk that fluid absorbed on a central portion of a flat mask may come into contact with the wearer's mouth and nasal openings.
Disposable masks made of fibrous webs molded into a cup-shaped configuration are also well known. Examples are described, for example, in U.S. Pat. Nos. 5,012,805, 4,807,619, 4,856,509, 4,850,347, 4,600,002, 4,536,440 and 3,333,585. Molded masks generally retain their cup-shaped configuration and in normal use the central portion of the mask does not collapse and come in contact with the wearer's mouth during inhalation.
The term "respirator" is often applied to a closely-fitting disposable face mask that has a relatively high filtration efficiency and that is used in areas such as construction or industrial settings where protection is desired from inhalation of sub-micron particulates that tend to remain suspended in the atmosphere for relatively long periods. Over the years, considerable effort has been expended to improve the filtering efficiency of respirators in order to reduce the amount of inhaled airborne contaminants. In this regard, effort has been directed toward improving the seal between the edge of the respirator and the wearer's face so that the substantial majority of the inhaled air does not bypass the filter media. Generally, cup-shaped molded respirators are preferred in instances where relatively high concentration levels of contaminants are present because the edge of the respirator can be brought into line contact with the user's face to establish a better seal than generally exists during use of flat masks.
Molded disposable masks and respirators are sometimes made of one or more fibrous layers that have been coated with a resin to enhance stiffness and help retain the molded, cup-shaped configuration. The resin-coated layers often adhere to each other after the molding process. Masks and respirators having one or more relatively stiff layers can be provided with one or two strong head straps that pull the mask or respirator tightly against the face to establish a good seal.
Disposable face masks and respirators are sometimes provided with a peripheral rib, seam or other structure in an attempt to achieve continuous contact of the edge of the respirator with the wearer's face. For example, U.S. Pat. No. 3,333,585 describes a fibrous mask with an edge covered by a bias fabric edging tape to make a softer fit. U.S. Pat. No. 4,600,002 describes a multiple-layer respirator stitched together with a binder strip folded over its edges. Edge structure that is relatively stiff may assist in maintaining the mask or respirator in a cup-shaped configuration.
One commercially available respirator (no. 8710, 3M) has an inner and an outer shaping layer with a filtration layer sandwiched between the shaping layers. The three layers are not adhered to each other by a resin coating; instead, a peripheral edge portion of the respirator is subjected to heat and pressure to establish a fused-together, bonded contact line closely adjacent the peripheral edge of the respirator.
Respirators with edge seals or bonded edge regions, like respirators with multiple layers bonded together, are often preferred for use in atmospheres with hazardous concentrations of suspended particulate matter. However, in medical and dental fields, the atmosphere is often relatively free of suspended particulates and personnel are instead concerned with droplets of bodily fluids such as saliva or blood, or small particulates that may be temporarily projected through the air. Dental personnel, for example, often work in close proximity to the patient and may wish to protect themselves from the patient's saliva that may be splashed or splattered about. Additionally, dental drilling procedures may cause pieces of the patient's tooth or old restorations to be propelled in the direction of the dentist or dental assistant.
Medical and dental personnel who wear face masks on a regular basis tend to wear such masks for extended periods of time, often over substantially the entire working day. Consequently, such individuals prefer a mask that is very comfortable and does not irritate the skin. Further, the availability of comfortable face masks may provide an inducement for some individuals to wear such masks more frequently and continuously than might otherwise be realized.